Octopamine Receptors in the Head of the Larva of the Common Cutworm, Spodoptera litura FABRICIUS (Lepidoptera: Noctuidae): Effects of Agonists and Antagonists

Abstract

Octopamine elevated cAMP level in head membranes of common cutworm (Spodoptera litura) larvae in a concentration-dependent manner, indicating the activation of receptor-linked adenylate cyclase. Several octopamine analogues, in which the hydroxyl groups of octopamine are replaced by other groups such as a chlorine atom, also showed agonist activities comparable to that of octopamine. However, no activation was seen with norepinephrine and dopamine. The rank order of potency of known agonists was : naphazoline >__- octopamine >__- 2-(2, 6-diethylanilino)-2-imidazoline >__- de-N-methylchlordimeform > clonidine > tolazoline. Mianserin appeared to be the most potent antagonist, although clear differences in potency between tested antagonists were not observed. The head of larval S. litura appears to contain heterogeneous octopamine receptors, with properties somewhat different from those of other insects.